Field of the Invention
The present invention relates to a resin discharge mechanism for use at a time of discharging a resin material mixed in mixing equipment to the outside of the mixing equipment for a sampling inspection or the like.
Description of the Related Art
Generally, a manufacturing plant for general-purpose polyolefin-based resins is equipped with a mixing and pelletizing apparatus for pelletizing the materials of these resins. This mixing and pelletizing apparatus is configured to include mixing equipment such as a continuous mixer that mixes these resin materials and a pelletizer that pelletizes the resin materials mixed by the mixing equipment. For example, the continuous mixer includes a cylindrical barrel provided horizontally and a pair of mixing rotors inserted into this barrel for mixing a material. A feed portion that supplies the material such as polymeric resin pellets is provided on one side of the barrel in a longitudinal direction in the continuous mixer, and the material supplied to the feed portion is fed to a mixing portion provided halfway along the barrel in the longitudinal direction. The mixing portion mixes the material between the paired mixing rotors with a shear force applied to the material, and feeds the melted material by the mixing to a drawing portion (mixing-degree adjustment portion) provided on the other side of the barrel in the longitudinal direction. The drawing portion adjusts the mixing degree by increasing (boosting) the internal pressure of the material. In this way, the material for which the drawing portion adjusts the mixing degree is fed to a post-processing portion from a discharge portion located downstream of the drawing portion via a gear pump or the like. (Refer to Hotani Shin and Yoshinori Kuroda (2008), “Continuous Mixers and Twin-screw Extruders for Polyolefin Finishing”, R&D Kobe Steel Engineering Report, Vol. 58, No. 2 (August, 2008), pp. 74-80; and Nakata Yoshiaki, Nobuhiro Yamasaki, Shoji Yasuda, and Kazuo Iritani (2005), “LCM Mixing and Pelletizing System for Polyolefin”, R&D Kobe Steel Engineering Report, Vol. 55, No. 2 (September, 2005), pp. 114-118.)
In the mixing equipment such as the continuous mixer described above or an extruder, it is often required to extract and inspect the mixed resin material before processing the resin material into finished products to determine whether the mixed resin material satisfies a desired mixing degree. In this case, it is necessary to additionally provide a resin discharge mechanism (also referred to as “diverter valve”) for extracting a part of the resin material that is not fed to the gear pump or the like yet as an inspection sample to the outside of the barrel.
For example, as shown in FIG. 6, a resin discharge mechanism 101 provided in conventional mixing equipment includes a resin discharge passage 116 (indicated by a black arrow in FIG. 6) provided on and open to a material transport channel 115 (indicated by a white arrow in FIG. 6) for feeding a mixed resin material from within a barrel 103 toward a gear pump and communicating the inside of the barrel 103 with the outside of the barrel 103, and a slide bar 117 closing or opening the resin discharge passage 116 by moving across this resin discharge passage 116. This slide bar 117 is capable of closing the resin discharge passage 116 by sliding in one direction by means of a hydraulic cylinder 120 or the like, and opening the resin discharge passage 116 by sliding in the other direction.
However, the inside of the barrel 103 is far higher in temperature than the outside thereof since the resin material is mixed with the shear force applied to the resin material and the high-temperature resin material plasticized as a result of the mixing flows in the barrel 103. Owing to this, the tip end side of the slide bar 117 closer to the inner surface of the barrel 103 (chamber) is higher in temperature than the base end side of the slide bar 117 closer to the outer surface of the barrel 103. As a result, a large temperature difference is generated between the tip end side and the base end side of the slide bar 117. This temperature difference generated in the slide bar 117 disadvantageously and often causes the tip end side of the slide bar 117 to be thermally expanded more greatly than the base end side thereof.
If the slide bar 117 is to slide with the diameter of the slide bar on the tip end side increased after the tip end side is thermally expanded more greatly than the base end side, the thermally expanded tip end side of the slide bar 117 is caught in a chamber side in small thermal expansion (tip-end-side opening edge of a guide bush 119). As a consequence, failures such as galling occur to the slide bar 117 and the chamber side, or even worse, the slide bar 117 cannot be pulled out from the chamber side, resulting in malfunctioning or the like.
Needless to say, the opening diameter of the chamber side can be set large enough in preparation for the possible increase in the diameter of the slide bar 117 on the tip end side due to the thermal expansion. To set the opening diameter large enough causes, however, the following problems. The resin material highly possibly enters the clearance between the slide bar 117 and the chamber side. The resin material entering the clearance is solidified or seized within the clearance, and remains as foreign matters. The resin material entering the clearance, in turn, disadvantageously causes galling or malfunctioning.